I know that Selmer mark VI saxes have a year of manufacture reputation and the earlier years of production are considered the better saxes, but does the same opinion apply to the RC? Were there preferred periods of production?

I haven't seen any specific data on this, however based on the logic that at one stage the R13 and RC were the top professional models produced by Buffet until they started to try and move the market (and price) upwards by introducing the Prestige versions and the even later Festival Divine etc etc. then the earlier models should on average be better that the "down-graded" later production.

My teacher told me a brief time when Buffet wasn't doing so well so during the early 2000s, they didn't make the best clarinets which is why they're trying to make a new look for themselves with the new logo and all the new lines of instruments. He told me this a while back so I might have twisted some of the words. Please correct me of I'm wrong!

If you have information on which years of the MKVI saxophone production were best, it would be good to know. It would also be very interesting to learn which years of the Buffet R13 were best. Please post such information if you have it.

Wes - many believe the five digit mark VIs were the best and these are the early ones. I have a 1970 mark vi tenor which is an amazing horn and I don't have an opinion regarding the argument.
My 1995 RC is a wonderful clarinet and is every bit as good as the day it was made.
Caroline's earlier comment is an interesting one though.

Yes, I own five MKVI Selmer saxes, including tenors from 1965 and 1964, but I have never had any opportunity to try others. Thus, even though they are good instruments, there is no basis for making comparisons. Your 1995 Buffet clarinet may even be better than new!

It's common to identify the Golden Age for R13's with early 1960s to early 1980s (serial numbers roughly 70,000 - 200,000). Since the RC only appeared in 1975, you might guess that the very early RCs would be the best. I play a 1979 RC and really like it, although the keywork is a bit worn. But I had a chance to buy a 1978 model in better condition and passed: it sounded very different, and clearly had a different design to the 1979 one (couple of mm difference in length of the lower joint). So they were tinkering with the design then, which makes blanket statements hard. All you can be sure about is the usual stuff: that the quality of wood and keywork prior to the early 1980s will be better than today - even the Prestige-level instruments. I've tried quite a few recent RCs, both Prestige and non-Prestige, and I feel the 1979 instrument sounds better - but probably no two players would agree on that.